1. Field of the Invention
The present invention relates to laboratory glassware and plastic ware and the filtration of liquid substances and the storage of filtrate.
2. Description of the Prior Art
There presently exists a laboratory liquid filtration unit which employs a polystrene filter cup with a cover, a support platform located beneath the cup, a nitrocellouse membrane filter positioned between the cup and support platform and a polycarbonate receiver with a receiver cap. U.S. Pat. No. 3,295,686 describes one embodiment of such a device, but another embodiment is also commercially available which has a downwardly opening outlet below the filter. This outlet is slipped over a smooth necked receiver flask. The commercial filter unit includes a side arm arranged for connection to a vacuum source below the level of the filter membrane. Liquid in the filter cup atop the membrane may thereby be drawn more rapidly through the filter by depressurizing the volume below the filter membrane and within the receiver flask.
The commercial embodiment of filter units of this type have several distinct disadvantages. The receiver flasks provided for use in collecting the liquid filtrate are not the flasks typically utilized for the storage of filtrate by laboratory researchers and technicians. Conventional storage bottles for the collection of liquid filtrates are widely employed in laboratories throughout the country. However, these conventional storage bottles are typically formed of glass with an upwardly opening mouth that is threaded externally to receive a screw cap. Two screw cap sizes 38-430 and 33-430 are widely used throughout the laboratory glassware industry. Conventional glass storage bottles of 125 ml, 250 ml, 500 ml and 1000 ml are the storage bottle sizes typically used in research laboratories for the storage of liquid filtrates.
In conventional practice, a vacuum filtration unit of the type described is employed to filter a liquid medium and temporarily collect the liquid filtrate in the smooth necked receiver flask supplied with the filter unit for this purpose. However, in conventional practice in most laboratories the contents of the receiver flask are shortly transferred to the more conventional screw necked storage bottles which are more suitable for storage of liquids. During the course of this transfer, there is a considerable likelihood of contamination of the liquid filtrate due to exposure of the liquid during the transfer process. Furthermore, a transfer of filtrate in this manner alters the volume of filtrate, since a certain amount of the filtrate is enevitably left behind in the temporary filtrate collection receiver. This represents a considerable inconvenience when the stored filtrate is to be utilized, since a recorded measurement of the volume of filtrate orginally collected must be maintained, and that record must be referred to in later work. It is much more convenient, according to the present invention, to merely observe the level of the filtrate in a conventional storage flask, since that level is accurate when the adapter of the invention is utilized.